Automatic headlight dimmer systemhigh voltage switching



Nov. 20, 1956 c. w. MILLER ET AL 2,771,559

AUTOMATIC HEADLIGHT DIMMER SYSTEM-HIGH VOLTAGE SWITCHING Filed Sept. 4, 1952 2 Sheets-Sheet 1 as: A

S & Inventors l a @6222 esZQJ/FZZ WW Attorneys Nov. 20, 1956 c w. MILLER ET AL 2,

AUTOMATIC HEADLIGHT DIMMER SYSTEM-HIGH VOLTAGE SWITCHING 2 Sheets-Sheet 2 Filed Sept. 4. 1952 5 S m m 0 $5 z United States Patent AUTOMATIC HEADLIGHT DlMlVIER SYSTEM HIGH VOLTAGE SWITCHING.

Charles W. Miller and Harold E. Todd, Anderson, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application September 4, 1952, Serial No. 307,818

11 Claims. (Cl. 315--83) This invention relates to automatic switching means and more particularly to light controlled switching means for the headlamp filaments of automotive vehicles.

In automatic light controlled systems for the dimming of vehicular headlamps, on normal highway driving with no approaching vehicles, the headlamps are on upper or high beam, so that the driver may see as far ahead of the vehicle as possible. Upon the approach of an oncoming vehicle, the latter will reach a point of approach such that the light falling on the photosensitivie pickup uni-t will be sufiicient to cause relay actuation and switching of the headlamps to low beam. As soon as that occurs the oncoming driver, in courtesy, switches his lights to low beam and the amount of illumination falling on the pickup unit is materially reduced. Provision must, therefore, be made at this time to hold the lights on low beam with a lower intensity of illumination falling on the photocell. One manner of accomplishing this result is to change the sensitivity of the complete system so that whenthe switching means moves to lower beam position, the sensitivity of the system is increased so that a much smaller amount of light falling on the pickup unit is needed to hold the switch in lower beam position than was initially required to move it to that position.

One manner of accomplishing this, result is shown and described in a copending application Serial No. 248,498, filed September 27, 1951, in the names of Charles W. Miller, Harold E. Todd and George W. Onksen, in which the sensitivity of the amplifier is varied.

It is therefore an object in making this invention to provide means for varying the sensitivity of an automatic headlamp dimming system between high beam and low beam positions.

It is a further object in making the invention to provide in a light actuated automatic headlamp dimming system means for varying the potential applied to the photosensitive means between high beam and low beam positions.

It is a still further object in making this invention to provide means for switching resistances in the power supply circuit to a photosensitive means between difierent switch positions controlled thereby.

With these and other objects in view which will becomeapparent as the specification proceeds, our invention will-be. best understood by reference to the following specification and claims and the illustrations in the accompanying drawings, in which:

Figure 1 is a circuit diagram of the electrical system of anautomatic headlamp dimming system embodying our invention;

I Figure 2 is a circuit diagramof a portion of the power supply to the photosensitive tube showing a modified formof our invention;

- Figure 3 is a circuit diagram of a portion of the control circuit showing a'further modified form of our invention; and

A Figure 4 is a circuit diagram of a portion of a control 2,771,569 Patented Nov. 20, 1956 circuit showing a still further modified form of our invention.

Referring now more particularly to Figure 1, there is shown therein at 2 a main low voltage D. C. power line which extends from a battery (not shown) to a vibrator power supply 4 in which the D. C. is changed to A. C. and applied to the primary 6 of a transformer 8. High voltage secondary winding 10 has one terminal connected through line 12 to anode 14 of a high-wave rectifier 16. The cathode 18 of the rectifier is connected to the filament 20, one side of which is grounded and the opposite side connected to line 2. The other terminal of the secondary winding 10 is connected through line 22 to one terminal of a plurality of resistors 24, 26, 28 and 30 in series relation which form a potentiometer. The opposite terminal of the last resistor 30 is grounded. A condenser 32 is connected between line 22 and ground to act as a smoothing filter.

A second secondary coil 34 of transformer 8, producing a lower voltage than coil 10, supplies power for the sensitive relay 36. One end of the winding 34 is connected through line 38 with one terminal of the relay winding 40, and the opposite terminal of the latter is connected through line 42 to the anodes 44 and 46 of the amplifying tube 48. A condenser 50 is connected directly across the relay coil 40. The switching means, comprising a portion of the relay 36, consists of two movable arms 52 and 54 which are mechanically secured to move together, as indicated by the dash and dotted line between the two, and move in the same direction when affected by the relay coil 40. Movable arm 52 is directly connected through tie line 56 with power line 2. Movable arm 54 is connected through tie line 58 with the movable tap 60 on resistance 26. Movable arm 52 is adapted to oscillate between fixed contacts 62 and 64, the first contact being unconnected electrically and acting only as a physical stop and the second contact, namely 64, being connected to line 66 which extends to a fixed contact 68 in the conventional foot switch 70. The movable arm 54 of the relay is adapted to, in one position, engage stationary contact 72, which is connected through tie line 74 with adjustable tap 76 on resistor 24.

Interconnecting line78 extends between tie line 74 and one terminal of a resistance 80, the opposite terminal of which is connected through a series resistance 82 to ground. An adjustable tap 84 on the resistor 80 is directly connected to line 86 supplying power to the cathode and various dynodes 88 of the photomultiplier tube 90. The anode 92 of the photomultiplier tube is a connected to output line 94 which extends to control grid 96 of the first triode section of the amplifier tube 48, and also through resistance 98 to main line 2. A condenser 100 is connected in parallel relation with resistor 98. The cathode 102 of the first triode section of the tube 48 is directly connected to line 2.

Tie line 103 extends between line 2 and line 104, which in turn connects stationary contact 106 of the conventional foot switch 70 and movable armature 108 of the power relay 110. Movable armature 108 oscillates between stationary contact 112, which is connectable to the upper beam filaments of the headlamps and stationary contact 114, which is connectable to the lower beam filaments. Relay coil 116 of the power relay has one terminal connected to ground and the other terminal connected through line 118 to movable switch arm 120 of the conventional foot switch 70. The second triode section of the amplifier tube 48 is connected as a rectifying diode due to the fact that the grid 122 and cathode 124 are connected together and through line 126 to stationary contact 128 of the auxiliary overriding foot switch 130, the movable switch arm 132 of which is grounded. Relay switch 108 is spring biased as shown to a position away from the relay coil, and therefore unless the relay coil is actuated, it assumes this position. Relay 52-54 is also spring biased, but is shown in its closed position.

n the operation of this system, when the various switches between the supply battery, not shown, and the power line 2 are closed, power will be supplied to the transformer secondaries 10 and 34. The amount of voltage applied to the photomultiplier tube 90 will be determined by the settings of the adjustable taps 76, 60 and 84- and the positions of relay armatures 52-54. The voltage supplied to the photomultiplier tube during high beam operation when the sensitive relay 36 is energized will be determined by the joint settings of the adjustable taps 76 and 6t and any more minor adjustments by the tap 84. The setting of the voltage supplied during those period of operation when the headlights are on dim will be determined by the setting of the adjustable tap 76 alone on resistor '24 with minor adjustments of tap '84.

Assuming that the proper positions of all three of these taps has been determined and that the system is energized, the switch members 52-54 will be in the positions shown. Power is at that time supplied to the photomultiplier tube from the tap 76 on the potentiometer with that section between taps 76 and 6t) shunted out by the closure of switch %72, and the first triode section of the amplifier 48 is conducting to permit relay coil 40 to hold movable arms 52 and 54 in the position shown against the pressure of the biasing spring. If a car approaches and sufiicient light falls on the photomultiplier tube 90 to increase the current flow therethrough, then the voltage on the grid 96 of the amplifier tube 48 will decrease until at a particular point the current through the tube will be sufficiently reduced to cause the coil 40 to release its armature contacts.

When this occurs the circuit to power relay 116 is completed by armature '52 moving into engagement with stationary contact 64. Coil 116 will attract its armature 108 against the biasing spring pressure, causing arm 108 to engage stationary contact 114 and disengage contact 112. This breaks the circuit to the upper beam filaments and completes the circuit to the lower beam filaments and the lights will be energized on low beam. At the same time the movement of the second armature 54 of the sensitive relay opens the circuit shunting a portion of the resistors determined by the setting of the adjustable taps 76 and 60, thus increasing the potential to the photomultiplier tube and making it more :ensitive, so that its output will be increased sufficiently to maintain the sensitive relay deenergized, even though the amount of light falling on the photosensitive cell decreases due to the oncoming drivers dimming his lights.

Operation of the conventional foot switch 70 from the position shown to that in which the movable arm 120 engages stationary contact 106 will, of course, manually connect coil 116 to the low voltage D. C. power and operate its armature to the low beam position. Overriding switch 130 is operative when the automatic system has switched to low beam position and the output from the photomultiplier tube on line 94 maintains grid 96 at such a potential that there is insufficient conduction through the tube to energize the relay coil 40 sufficiently to maintain its armature against spring bias.

Then by the operators closing switch 132, 128, the rectifier formed by the second triode section will conduct a sufiicient amount of power so that the coil 40 may independently attract its armature, switching the lights back to upper beam as long as this switch is closed, but permitting return to lower beam if, when released, there is sufiicient light radiation falling on the photomultiplier unit.

Figure 2 discloses a modification of the system shown in Figure l in that the resistor 82 and its ground connection are removed from the system. Variable resistance -84 is then used alone directly in the circuit to the dynodes of the photomultiplier tube. Otherwise the operation is not varied in any way.

Figure 3 shows a further modified form in which, instead of shunting out a portion of the potentiometer between the high voltage line and ground by the operation of the sensitive relay switch, a potentiometer in series circuit to the dynodes is shunted by such operation to provide a fixed ratio between the voltage applied to the photomultiplier tube when the lights are on upper beam as that applied when on lower beam. Specifically, Figure 3 discloses the same power transformer 8 and the two secondaries 10 and 34, the high potential lead 22 of the winding 10 being connected to one terminal of a resistor 134, which is connected in series relation through resistors 136 and 1449 to ground, the three forming a potentiometer. Variable tap 142 on resistance 134 is directly connected to a variable resistor 144 and also to tie line 146. The opposite terminal of variable resistance 144 is connected to line 148, which terminates at one terminal of potentiometer 80. The adjustable tap 84 is connected as before to tube supply line 86. Line 146 is connected to stationary contact 150 which cooperates with movable armature 54 of the sensitive relay 36. Armature 54 is connected through line 152 to tie line 148.

It will thus be obvious that when the sensitive relay 36 is deenergized and the biasing spring forces the two movable armatures 52 and 54 toward the right, as viewed in Figure 3, that variable resistance 144 will be shunted out, changing the voltage applied to the photomultiplier tube through supply line 86, applying more voltage to the photomultiplier tube and rendering the system more sensitive. Thus, instead of shunting out a portion of the potentiometer, a variable resistance directly in series is shunted out. Adjustments for the level of operation of the photomultiplier tube may, of course, be made as previously by moving adjustable tap 142 on resistor 134, varying the. resistance 144, and adjusting tap 84 on resistor 80.

Figure 4 diifers from Figure 3 in that the right-hand terminal of resistor 80 is connected through resistance 82 'to ground, as in the circuit shown in Figure 1. In this instance, however, the variable resistance 144 in series with resistor 80 is shunted out by relay action to change the voltage applied to the photomultiplier tube.

It will, therefore, be obvious that we have devised a control system in which the sensitivity of the complete system is varied by shunting out resistance in the power supply circuit to the light sensitive element so that the same is more or less responsive during desired portions of the operating cycle.

We claim:

1. In a control system for multibeam headlamps, a source of power, switching means connected to the source and to the headlamps alternately connecting said source to the diflerent filaments of the headlamps, control means actuating the switching means connected to the source of power and including a light sensitive means, potentiometer means connected between the sources of power and the light sensitive means to supply voltage to the light sensitive means and additionl switching means actuated by the control means connected in shunt to a portion of the potentiometer means between the source of power and the light sensitive means to vary the voltage supplied to the light sensitive means between the different filament energizing positions.

2. In a control system for multibeam headlamps having an upper and a lower beam filament, a source of power, switching means connected to the source and to the-filaments alternately connecting said upper and lower beam filaments to the source of power, control means for the switching means connected to the source of power and including a light sensitive means, and means connected between the source of power and the light sensitive means actuated by the control means simultaneously with the switching means to vary the potential applied to the light sensitive means as the headlamps are switched between upper and lower beam filaments.

3. In a control system for multibeam headlamps having upper and lower beam filaments, a source of power, switching means connected to the source and to the filaments alternately connecting the source to the filaments, control means for the switching means including photoelectric means, means connected between the source of power and the photoelectric means to vary the potential applied to the latter and compound switching means connected to the photoelectric means and to the means to vary the potential and controlled by the photoelectric means to simultaneously actuate the first-named switching means and the means to vary the potential applied to the photoelectric means.

4. In a control system for multibeam headlamps having upper and lower beam filaments, a source of power, switching means connected to the source and to the filaments alternately connecting the source to the filaments, photoelectric means connected to the source of power, resistance means in the connection between the photoelectric means and the source of power, second switching means shunting said resistance, and relay means connected to and operated by the photoelectric means actuating both the first and second switching means to simultaneously change headlamp beam illumination and the potential applied to the photoelectric means.

5. In a photosensitive control system for switching dependent upon the amount of illumination present, a source of power, a photosensitive means, resistance means connected between the source and the photosensitive means, shunting means for a portion of the resistive means, a first switching means in the shunting means, a second control switching means, and relay means connected to the source of power and the photosensitive means and controlled by the output of the photosensitive means operating both the first and second switching means simultaneously.

6. In a photosensitive control system for switching dependent upon the amount of illumination present, a source of power, a photosensitive means, means interconnecting said source with said photosensitive means including a potentiometer, a shunting circuit connected around a portion of the potentiometer, switching means in the shunting circuit, control switching means, connected to the source of power and to means to be controlled, amplifying means connected to the output of the photosensitive means, and relay means connected to the amplifier output and to the source of power actuating the switching means in the shunting circuit and the control switching means simultaneously.

7. In a photosensitive control system for switching dependent upon the amount of illumination present, a source of power, a photosensitive means, means interconnecting said source with said photosensitive means including variable resistance means, a shunting circuit connected around a portion of the variable resistance means, switching means in the shunting circuit, control switching means connected to the source of power and to means to be controlled, amplifying means connected to the output of the photosensitive means, and relay means connected to the amplifier and to the source of power actuating the switching means in the shunting circuit and the control switching means simultaneously.

8. In a light responsive control system, a multiple position control relay, a source of power connected thereto, variable resistance means connected to said source of power, a light responsive member connected to said variable resistance means providing for adjusting the voltage applied thereto, a shunting circuit connected around a portion of the resistance means, and switching means connected to the source of power and the light responsive means and operated by the output of the light responsive means to control the relay operation and the shunting circuit to vary the potential applied to the light responsive means dependent upon switch position.

9. In a control system for multibeam headlamps having an upper and a lower beam filament, a source of power, first switching means connected to said source and to said filaments to alternately energize the same, potentiometer means having adjustable taps connected to said source of power, a shunting circuit interconnecting said taps, second switching means in the shunting circuit to open or complete the same, light sensitive means connected to the shunting circuit to supply power to said light sensitive means from the potentiometer means, amplifier means connected to the output of the light sensitive means, and relay control means connected to the output of the amplifier means and to the source of power and controlled by the fiow of current therethrough operating both the switching means to simultaneously change from low to high beam filament energization and change the potential applied to the light sensitive means.

10. In a control system for multibeam headlamps having an upper and a lower beam filament, a source of power, first switching means connected to said source and to said filaments to alternately energize the same, potentiometer means having adjustable taps connected to said source of power, a shunting circuit interconnecting said taps, second switching means in the shunting circuit, to open or complete the same, light sensitive means connected to the shunting circuit to supply power to said light sensitive means, variable resistor means in the connection between the light sensitive means and the shunting circuit to further adjust the power supply to the light sensitive means for actuating said switching means, and control means connected to the light sensitive means operating both switching means simultaneously.

11. In a control system for multibeam headlamps having an upper and a lower beam filament, a source of power, first switching means connected to said source and to said filaments to alternately energize the same, potentiometer means connected to said source of power, conductive means including variable resistance connected to the potentiometer means upon which a voltage is developed, light sensitive means connected to the conductive means and supplied with operating voltage therefrom, a shunting circuit including a second switching means connected around the variable resistance, and control means actuating both said switching means connected to said light sensitive means to operate both switching means.

References Cited in the file of this patent UNITED STATES PATENTS 1,942,289 Hipp Jan. 2, 1934 1,981,985 Braselton Nov. 27, 1934 2,380,486 Willis July 31, 1945 2,476,389 Schmidt July 19, 1949 2,507,436 Dole May 9, 1950 2,598,420 Onksen May 27, 1952 

